These H5 (heading level 5) don't allow for a good headings hierarchy and shouldn't be headings in the first place. Each group of options has now its own fieldset and legend.
In `render_screen_options()`, introduce two new "render" methods: `render_meta_boxes_preferences()` and `render_list_table_columns_preferences()` for consistency with already existing render methods and cleaner code.
Props joedolson, afercia.
Fixes#33646.
Built from https://develop.svn.wordpress.org/trunk@34991
git-svn-id: http://core.svn.wordpress.org/trunk@34956 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Andrea Fercia
Scott Taylor
Drew Jaynes